Hemoglobin determination is one of the most frequently performed tests in hospitals. Anemia, or a decrease in hemoglobin concentration, is a sign of an underlying disease process. Mild anemic states often cause no symptoms because of the body's ability to compensate for the deficiency in hemoglobin, at least on a short term basis. With increasing severity of anemia, however, the resulting increased cardiac stress may cause tachycardia, shortness of breath, and headaches. In its most severe form, anemia may lead to coma and death.
A commonly used determinant of hemoglobin concentration in whole blood is hematocrit. Hematocrit is generally defined as the volume fraction of whole blood that is occupied by red blood cells. The hematocrit of a normal healthy person is generally about 45% (about 42 to 52% for men and about 36 to 48% for women). Much lower values than the foregoing are a sign of anemia. Hematocrit can be determined by centrifuging a whole blood sample in a volumetrically calibrated centrifuge tube (or capillary centrifuge tube) to settle all of the red blood cells at the bottom of the tube, leaving the plasma at the top. A “buffy coat” of white blood cells just above the red blood cell layer indicates complete separation. The volume % of red blood cells is then calculated by dividing the volume occupied by the red blood cells by the total volume, and multiplying by 100. Plasma and red blood cells must be disposed of after the test is complete. The test also requires a centrifuge, making it impractical for home use.
The standard laboratory hematocrit test generally requires that the blood be drawn and tested by a clinical technician or other health care provider. Biological waste disposal problems are generated as well. There is an ongoing need, therefore, for a hematocrit testing device that can be utilized by an individual, at home, or by health care professionals, which is relatively simple to use, can be performed with a small, capillary blood sample, that does not require use of a centrifuge, and that minimizes and simplifies blood disposal after the test is complete. The hematocrit measuring device of the present invention fulfills this need.